Question: There are $4$ more books on the top shelf, shown below, than on the bottom shelf. How many books are on the bottom shelf?
Explanation: We can take away ${4}$ books from the ${7}$ on the ${\text{top shelf}}$ to see how many are on the ${\text{bottom shelf}}$. ${7} - {4} = {\Box}$ There are ${3}$ books on the bottom shelf.